Two-dimensional Joint Inversion Of Magnetotelluric And Geothermal Data

There are many geophysical methods for geophysics,and each process can only invert a single underground physical property parameter.Joint inversion is based on the distribution of physical parameters of underground geological bodies with similar structures.It can reduce the multi-solution of single method inversion through two or more methods of inversion.In electrical exploration,the magnetotelluric sounding method is a crucial branch method with the advantages of considerable detection depth,low cost,and simple work,which is widely used in the field of geophysics.Geothermal energy is a typical representative of a new type of energy.It is a clean,low-carbon,widely distributed,and resource-rich renewable energy source.In recent years,Hot Dry Rock geothermal resources have become a new research focus,and their burial depth and the difference characteristics of physical property parameter provide the possibility for joint inversion.The article studies the forward and inversion of the 2D magnetotelluric based on the unstructured triangular grid.The article introduces the advantages and characteristics of the triangle grid and the difference from the rectangular grid in calculations,use Triangle code to split the area,and compares with the reference results of the standard model to verify the correctness of the forward code.The inversion part uses the LBFGS,introduces the origin and advantages of the method,and focuses on the derivation of model items suitable for unstructured grid inversion.The article establishes a complex anomaly model to perform forward and inverse calculations to verify the advantages of unstructured grids.The geothermal part begins from the law of conservation of energy,deduces the heat conduction equation applicable to the geothermal field,conducts a numerical simulation of the geothermal field.The influence of the thermal conductivity distribution on the geothermal field and the formation conditions of the Hot Dry Rock geothermal resources are studied through the numerical simulation of the geothermal field.The article uses the temperature values at different locations and depths in the ground as observation data to invert the distribution of underground thermal conductivity,for discussing the possibility of inversion of geothermal data.By comparing the results of the two single-method inversions,the joint inversion section discusses the inversion of the underground thermal conductivity distribution in combination with the magnetotelluric method when the number of drillings and depth information is limited.It is vital for exploring the Hot Dry Rock geothermal resources.